One of my Visual Studio 2022 extensions has dependencies on the nuget packages Microsoft.VisualStudio.SDK 17.0.32112.339 and Microsoft.VSSDK.BuildTools 17.7.2196. I obviously added them some years ago, and updated the BuildTools only once out of necessity. The current versions of these packages are 17.12.40392 and 17.12.2069, respectively. The current stable version of Visual Studio 2022 itself is version 17.12.
Question: If I update these dependencies to their latest versions, does Microsoft guarantee that the resulting extension (.vsix package) also works with older versions of Visual Studio 2022, for example VS 2022 17.7? I couldn't find anything to this regard in the documentation.
The error you got gave the right hint: generally no, newer packages won't support older versions. And for good reason: if we add a new API in a minor release, that'll be in that new package, but that won't exist in older versions.
One notable exception is the VSSDK.BuildTools package -- newer versions there can still target older versions of Visual Studio; sometimes you have to upgrade this one in your build to support newer build environments.